Combustion contkol



P 1934- J. c. ALBRIGHT 1,972,968

COMBUSTION CONilROL Filed May 9, 1932 last Furnace *6 (D Gas E 200 gokeOven 6S g F 1g Z 2. e

1 INVENTOR Carbon 0 2,0 100 Jogeph (Theoretical Air) Excess Air-Percent.1

- TTgiNEY Patented Sept. 11, 1934' UNITED STATES oomus'rron oou'raor.

Joseph C. Albright, Teaneck, N. .L, assigrior to Bailey Meter Company, acorporationof Delaware Application May 9, 1932, Serial No. 610,295 19Claims. (Cl. 236-14) This invention relates to combustion control, andespecially to the control of the supply of air for combustion to thefurnace of a vapor generator or to heating furnaces in general, whereinthe elements of combustion react to liberate heat, and where a pluralityof fuels may be fed the furnace simultaneously and in any proportion.

Ordinarily a single fuel is burned in the furnace and an indication ofcombustion efficiency may be had through obtaining the relation existingbetween a measure of the air flow and a measure of output such. forexample, as vapor outflowfrom a vapor generator. Such indication ofcombustion efiiciency may then be utilized as a guide for eithermanually or automatically controlling the supply of air for promotingcombustion.

Relation indicators have been known for showing the instantaneous valueof such relation, but have been used in connection with the burning of asingle fuel. In the combustion of a single'fuel at different rates ofoutput and at a predetermined desirable excess of air, a definite rateof flow of products of combustion will result for each rate of output.The value of the rate of flow, or its flow effect, or the relation suchas previously referred to, may be calculated for any given fuel; butwhen a plurality of fuels are burned simultaneously in a furnace and invarying proportions, the resulting volume of products of combustion willvary not only with the percentage of excess air and the ratingdeveloped, but also with the character of the fuels burned and theproportioning of the several fuels.

It is therefore a primary object of the present invention to control thesupply of air for combustion in the most eflicient manner, regardless ofthe rating developed or the proportionality of a plurality of fuelssupplied simultaneously for combustion.

It is a further object of the invention to provide a relation indicatorfor indicating as a guide to manual or automatic control of the supplyof air the relation instantaneously existing between a measure of theoutput of the furnace or of some variable factor in the operation of thefurnace and a measure of the airflow, taking into account theproportionality and characteristics of the various fuels simultaneouslyburned in any proportionality from zero to one hundred percent ofmaximum supply of each of the fuels; and furthermore, the excess air atwhich the fuels are burned.

Another object of the invention is to obtain a measure of the air flowfor the purpose of controlling the air supply, automatically taking intoaccount on such measure of the air flow a measure of one of the fuelswhere a plurality of fuels is burned simultaneously.

A still further object is to obtain a measure of one of a'plurality offuels burned simultaneously and cause such measure to effect acompensation of a measure of the air flow in relation to acharacteristic such as calorific value ofeach of the fuels separately soburned.

Still another object is to combine as a readable guide for manually orautomatically controlling the supply of air to a furnace, indications ofthe air flow and of one of a plurality of fuels burned simultaneously ina furnace, giving a resultant indication of air flow compensated forproportionality of fuels burned, their calorific value; and/or othercharacteristics of the combustion, such for example as percentage ofexcess air with which the fuels are separately burned.

As a preferred embodiment of my invention, I have illustrated and willdescribe the invention in connection with a steam generating boilerfurnace to which are fed for combustion two fuels simultaneously and inamounts which may vary from zero to maximum of either of the fuels.

In the drawing:

Fig. 1 represents a sectional elevation of a steam generator and itsrelated heating furnace,rshowing fuel and air supplying means, as wellas the system and apparatus of my relation indicator and control system,in somewhat diagrammatic fashion.

Fig. 2 represents a graph of the flow effect of the two fuels burned.

I illustrate at 1 a furnace arranged for heating a steam generator 2through the combustion within the furnace 1 of fuel fe'd thereto througha burner 3. The burner entrance to the furnace 1 is surrounded by an airbox 4 in common manner.

To the burner in the present embodiment is sup-- plied two fuelssimultaneously in varying amount,

namely, blast furnace gas through a conduit 5 and.

coke oven gas through a conduit 6, the former.

regulated in quantity rate of flow by a regulating valve '7, andthe'latter by a similar regulating valve 8. The throttling control ofthe valves '7, 8 may be by hand or automatically from steam pressure orotherwise, as desired; the same forming no part of the presentinvention. It is only contemplated that the fuel supplied through theburner 3 be in the'present embodiment composed of blast furnace gas andcoke oven gas in varying proportions from zero to maximum rate 'of flowof either.

The rate of air supply entering the furnace through the air box 4 andthe burner 3 is controlled. by the suction exerted upon the furnace of asta ck 9 having positioned therein a damper 10 through the agency of astop-start-reversing pilot motor 11 for controlling the draft.

Steam generated in the boiler 2 passes therefrom through a conduit 12 inwhich is positioned orifice 13 for causing a drop in pressure bearing adefinite and known relation to the rate of flow I mentsfidirectly.proportional to the rate of steam through the conduit and providing ingeneral a measure of the steam outflow from the generator.

Connected to the conduit 12 at opposite sides of the orifice 13 by meansof the pipes 14, 15 I show a rate of flow meter 16 having an indicatorarm 17 adapted to cooperate with an index 18 for advising the rate offlow of steam leaving the boiler through the conduit 12. Such a meter isillustrated as a known type, having a variable diameter liquid sealedbell whose wall is of material thickness whereby the quadratic relationbetween differential pressure across an orifice and rate of flowtherethrough is converted to a linear relation, to the end thatpositioning of the indicator 17 relative to the index 18 is in. equalincreof flow of steam from the boiler.

. At 19 I designate in general an air flow meter comprising primarily aliquid holding casing 26 relative to which is located a pivot support21. A beam 22 is adapted to be positioned around the pivot 21 in angularmovement, and such movement or positioning is indicated by a projectionat one end of the beam 22 relative to an index 23. From the beam 22 atopposite sides of the pivot 21 are suspended liquid sealed bells 24, 25to the undersides of which'i led respectively through pipes2'6, 27 thepressu -e existing at two points in the gas passage through the boiler2between which there is resistance to the flow of products of combustion,thus producing a pressure differential between the points of connectionbearing a known relation to the rate of flow of the air and gasestherethrough. Such pressure diifer ences, when applied to the undersideof the liquid sealed bells 24, 25 in the air flow meter 20, react on thebeam 22 as a resultant force tending to rotate the beam around its pivot21. Rotation is opposed by a displacer 28 suspended from the beam 22within a second liquid, preferably mercury, and the displacer of a shapeparabolic in function through whose agency the positioning of the beam22 in rotation around the pivot 21, as

= indicated on' the index 23, is by equal increments directlyproportional to the rate of flow of air and gases through the boiler 2.

Displacer 28, while in general of parabolic functional shape, may haveits shape modified therefrom, and furthermore, the displacer is providedwith means for being moved along the beam 22 relative to the pivot 21 tovary its moment arm.

, The general arrangement and purpose of the dis- 1 placer 28 is tocounterbalance or counteract the resultant force actin'& ponthe beam 22of the pressure differential e ective upon the bells 24, 25 whereby adesired relation is obtained between increments of indicator movementover the index 23, and increments of differential pressure existingbetween the points of connection of the pipes 26,27 with the boiler 2.

It will be observed that the pipe 27 connecting to the boiler at alocation closer to the stack than the connection of the pipe 26, leadsbeneath the bell 24 and exerts upon the bell 24 a suction ordownwardforce greater than the downward force applied beneath the bell 25. Thisdifferential in pressure will tend to cause a rotation of the beam 22 incounterclockwise direction around its pivot 21. Such a tendency torotate will be opposed by the lifting of the displacer 28 from themercury, producing an increasing weight upon the beam 22 adjacent thebell 25 to counteract the tendency for counterclockwiserotation. The

ishape of the displacer 28 is made in general such that the pressurediflerences exerted upon the bells 24, 25 bearing quadratic relation tothe rate of flow of air and gases through the boiler 2 will be indicateddirectly upon the index 23 as equal increments of rate of flow. I

By air flow through the furnace andboiler as measured by the air flowmeter 20 I mean not only air but all of the products or gases ofcombustion leaving the furnace through the stackv 9 and which areutilized for heating the genera-' tor 2 in their passage from thefurnace to the stack. When the proper calibration and adjustments havebeen made, the air flow meter 20, by measuring the rate of flow of allof the air and products of combustion leaving the furnace, will indicatethe rate of flow of air supplied for combustion.

It is known that a comparison of the rate of steam flow leaving theboiler as an indication of boiler output with the rate of airflowthrough the boiler comprises an adequate guide for manual or automaticcontrol of the supply of air for combustion to the related furnace. Itherefore connect the indicator arm 17 of the steam flow meter and theindicator arm 22 of the air flow meter through linkage for comparing theinstantaneous values of the steam flow and air flow and advising adeparture of the relation of instantaneous values from desired relation.

From the steam fiow indicator arm 17 I pivotally suspend a link 29pivotally joined at its lower end to one end of a freely floating beam30. From the beam 22 I suspend a similar link 31 pivotally connected atits lower end to a fioat- 1 ing member 32 intermediate the ends of themem- 110 ber 32.

One end of the floating member 32, namely (on the drawing) the righthandend, is pivotally connected to a link 33 dropped vertically downwardtherefrom, and whose purpose will be explained hereinafter.

The lefthand end (on the drawing) of the floating member 32 is pivotallyconnected through a link 32A to an extension 34 of a cam 35, which camis adapted for rotation or angular movement around a fixed pivot point36 The arrangement is such that assuming the link 33 stationary, thenvertical reciprocation of the link 31 raises andlowers the lefthand endof the member 32 and correspondingly tends to rotate the extension 34and cam 35 in one direction or the other in angular movement around thefixed pivot 36.

Bearing on the shaped surface of the cam 35 is a roller 37 adapted torise and fall substantially vertically as the cam 35 moves angularlyaround its pivot 36. The roller 37 is carried at one end of a beam 38pivoted intermediate its ends at a fixed pivot 39 and carrying acounterweight 40 for holding the roller 37 in engagement with thesurface of the cam 35. ,The beam 38 at 5 its other end forms anindicator arm adapted to cooperate with an index 41 and from the beam 38near the lefthand end (on the drawing) is suspended pivotally connectedthereto a link 42 which at its lower end is pivotally connected to therighthand end of the floating beam 30. Equal increments of verticalmovement of the link 31 will result in increments of vertical motion ofthe link 42, related thereto according to the shaping of the cam 35.

Pivotally connected to the. floating beam 30 at a point intermediate itsends is a link 43 connected to and for oscillation of a contact bar 44around a fixed pivot 45 intermediate the ends of the contact bar. Oneend of the contact bar/44"150 forms an indicator arm adapted tocooperate with an index 46 to show departure from predetermined positionin one direction or the other.

Carried by the contact bar 44 are one-half each of normally opencircuited contacts 4'7, 48 and the contact bar is connected through aconductor 49 with a main power line 50. The other half of the contact 47is connected through a conductor 51 with the motor 11, and the otherhalf of This positioning causes a close-circuiting' of the contact 4'7,completing a circuit comprising main power line 50, conductor 49,contact 47, conductor 51, motor 11 and conductor 53 to main power line54, whereby the motor 11 is energized for rotation in a direction toincrease the opening of the damper 10 and allow a greater flow of airthrough the boiler. Assuming that the rate of steam outflow remains thesame, then the increased flow of air through the boiler effective as anincreased pressure differential applied to the bells 24, 25 of the airflow meter 19 will cause an upward positioning of the indicator '22relative to the index 23 with an upward movement of the links 31, 42 andcontact bar 44 until contact 4'7 is open circuited, thus stoppingrotation of the motor 11, for the resulting air flow is then in desiredrelation to the increased steam flow. v

The operation is the same in reverse manner, should the rate of steamflow decrease from any value. Correspondingly, should the steam flowremain steady but for some reason such as change in wind across the topof the stack 9, the air flow through the boiler would increase ordecrease, then its action upon the air flow meter 19 and the links 31,42 would result in a positioning of the motor 11 in one direction or theother for an opening or closing of the damper 10 until again the airflow balances the steam flow in desired relation.

It will be observed that it is not necessary that the relation betweenair flow and steam flow be in 1 to 1 ratio, but through properadjustment of moment arms any desired and predetermined relation may beindicated or utilized for control. Proper adjustment as to size of thebells 24, 25, shape of the displacer 28, and moment arms of the bellsand displacer relative to the pivot 21 take care, for theparticulardesign and type of boiler, of the resistance between the points ofconnection at a given rate of output.

The indicator arms 1'7, 22 need not necessarily indicate relative toseparate indexes 18, 23, but

may readily be adapted to move relative to a common index or maycomprise co-related pen traces upon a single recording chart; it onlybeing necessary in a contemplation of my invention that a measure ofsteam be simultaneously observable for comparison as to desired relationor departure therefrom, and with the understanding that steam flow andair flow are used merely as examples of the variable characteristics inthe operation of the furnace. The positioning of the indicator arm 44relative to the index 46 denotes the presence of or de- 1 place ofreading'each at flow and a measure of. air flow parture from desiredrelationship between steam flow and air flow on a single index, or asabove stated, the indicator arms 1'7, 22 may comprise pens working on asingle recording chart over the same set of graduations and desirablyrecording at the same point on the chart when proper relationship isobtained. 7 Furthermore, the indicated relationship'between suchcharacteristics may be utilized as a guide for manual control of thesupply of air or as a part of an automatic control system. 1

I have described so far a steam flow meter and an air flow meter inco-relation, as would be adaptable to a boiler furnace wherein a singlefuel were burned, for example, blast furnace gas alone, through theburner 3. Assuming combustion with a constant percentage of excess airregardless of rate of operation, then the differential pressure existingthrough the boiler 2 and effective upon the air flow bells 24, 25 isindefinite quadratic relation with the rate of flow of air through theboiler. If, however, we should suddenly shift from burning all blastfurnace gas to a condition of burning all coke oven gas, and

in sufficient quantity of B. t. u. input to maintain the same steam flowoutput or B. t.-u. output of the boiler, and were the coke oven gasburned with the same percentage of excess air, then the pressuredifferential existing across the points of connection to the boiler andimpressed upon the bells 24, 25 would vary from that of the previousexample. This due to the fact that for a radically different fuel theproducts of combustion will vary, the one from the other, and what 1term the flow effect of the particular fuel will vary for the one fuelas compared to the other fuel.

If, for example, when burning blast furnace gas alone, the steam flowindicator read at 50% of maximum on the'index 18 and the air flowindicator read at 50% of maximum on the index 23, indicating a relationof the proper air flow for the fuel burned at a desired excess aircondition in the furnace, then upon a sudden shift to burning coke ovengas in proper B. t. u. quantity whereby the steam flow indicatorremained at 50% of maximum on the index 18, the air flow indicator woulddrop to some reading, for example 48% of itsmaximum, thereby indicatingthe difference in flow effect between the products of combustion of.blast furnace gas andthe products of combustion of coke oven gas at thesame Desirably in the operation of the furnace andboiler, the readingsof steam flow and air flow are to be kept in desired relation as a guideto hand or automatic control of air supply, and thus as'in the example,if the fuel were changed suddenly from all blast furnace gas to all cokeoven gas, the steam and air flow indicator arms in of their maximumwould now read 50 and 48 respectively, indicating to the operator or tothe automatic control a condition which would need correction in thedirection ofincreasing the supply of air so'that the air flow indicatorwould come up to a unity relation with that of the steam flow. However,if the air flow were so increased as to bring the air flow indicatorfrom 48 to 50 on its index, this actually would result in too great asupply of air,

and the excess of air for combustion would have increased over thedesired value, with corresponding loss of efficiency of combustion.

What actually is desired, is that the reading of the air flow indicatorarm when switching from one fuel to the other, should be compensated ormoved mechanically from 48 to 50 so that to the operator or to theautomatic control the proper relationship still exists, and nocorrection in air supply is needed. My invention primarily contemplatessuch a correction of the actual air fiow reading to take care of thedifference in flow effect produced through the burning of differentfuels, and the compensating means which I will describe wouldautomatically, upon the shifting of blast furnace gas to coke oven gas,mechanically move the air flow effect upon the floating beam 30 from theequivalent of its reading of 48 to an equivalent of its previous readingof 50, whereby is indicated that the proper supply of air exists throughthe position of the indicator 44 relative to the index 46. It is to beunderstood that the position of the indicator '44 relative to the index46 is for the guidance of the operator, or as through the contact'bar 44for the guidance of .automatic control to advise that the steam flowairfiow relation is as desired, or a departure from such desirablerelation.

1 Such a condition as I have described would ocour in the suddenshifting from the burning of one fuel to that of burning another wholly.However, I contemplate the possibility of burning the two fuelssimultaneously in varying proportions, in which event I must apply as acompensation to the air flow mechanism an'eifect proportional to theflow effect of one of the fuels when the air flow mechanism has beencalibrated for the burnihg of the other of the fuels, and suchproportion must be in accordance with the magnitude of the relativeproportion of the two fuels burned, or desirably in proportion to thetotal B. t. u. input from each of the two fuels.

Referring now to the drawing, Fig. 1, I show a fuel flow meter having aliquid containing case'56 relative to which is located apivot 57.Oscillatable around the pivot 57 is a beam 58 having suspended therefromat opposite sides of the pivot 5'7 liquid sealed bells 59, 60.

In the conduit 6 through which is supplied the coke oven gas to theburner 3, I position a pressure differential producing device such as anorifice 61 for causing a drop in pressure bearing a definiteand knownrelation to the rate of flow of coke oven gas through the conduit 6 andproviding a measure of the flow therethrough. At opposite sides 'of theorifice 61 I connect pipes 62, 63 leading respectively to the undersidesof bells 59, 60 and applying to the bells and as a resultant to the beam58. an effect proportional to the flow of coke oven gas.

I suspend from the beam '58 a displacer 64 adaptable for movement alongthe beam 58 to vary its moment arm relative'to pivot 57 and providing avariable counter-balancing effect for the force applied to the beam bythe bells 59, 60. The pressure at the inlet of the orifice 61 will I bethe greater, and efiective through the pipe 63 to the underside of thebell 60, will provide an' upward force tending to rotate the beam 58 inav counterclockwise direction around its pivot 57 relative to thesmaller force of the pressure on the downstream side of the orifice 61effective through the pipe 62' upon the underside of the bell 59. Suchtendency towards counterclockwise rotation of the beam 58 is opposed bythe pulling out of the mercury of the displacer 64. The displacer 64 ispreferably shaped in quadratic function so that a pointer formed at theend of the beam 58 ,will move along an index 65 in equal increments withincrements of rate of flow of coke oven gas through the orifice 61.

I show the lower end of the link 33 pivotally connected to the beam 58and vertically positioned thereby. It will be observed that therighthand end of the floating member 32 (previously considered as fixed)is adapted for vertical positioning with and by the beam 58 as a measureof coke oven gas rate of flow. Should the link 31 be stationary, then avariation in the percentage of coke oven gas burned or supplied to theburner 3 will cause a positioning of the member 32 around the lower endof the link 31 and correspondingly a vertical positioning of the link43. Thus the link 42 may be positioned vertically either by a change inrate of air fiow by the'fiow meter 19 or a changein rate of coke ovengas flow by the corresponding meter 55.

Interposed between the floating member 32 and the link 42 I have shownthe cam 35 and the parts related thereto, which is for the purpose ofallowing the fuels, regardless of their relative proportionality, to beburned with a different excess of air at one boilerrating than atanother boiler rating. This may be desirable, and often is desirable toprotect the furnace walls or other parts blast furnace gas, for example,the calibration of such air flow meter through varying the moment arm ofthe displacer 28, etc. may be adjusted to burn the blast furnace gas ata desired excess of air, for example, 15% over that theoreticallyrequired for combustion. Thus regardless of rate of B. t. u. output as,indicated by the steam flow meter, the air flow meter will indicate thesame reading in co-relation thereto when the rate of flow of the excessair and products of combustion through the furnace is proper for thedesired excess of air, with burning the right amount of blast furnacegas for. the heat liberation indicated. Thus we may say that the airflow meter.19 can be properly calibrated to burn blast furnace gas aloneunder a desired predetermined excess of air regardless of rating, andwhen such condition exists the air flow meter will indicate the same'percentage of its maximum index as does the effect upon the positioningof the floating member 32 is in accordance with the burning of the cokeoven gas at a definitepredetermined percentage of excess air regardlessof rating, which, for example, may be the same or a different percentageof excess air thanthat for which the air flow meter 19 is calibrated forthe buming' of blast furnace gas.

Thus I might so calibrate the air flow meter 19 that when'burning onlyblast furnace gas, the blast furnace gas is burned at an excess airpercentage of 18, and so calibrate the meter 55 in its linkage effectupon the member 32-that desirably the coke' oven gas were burned at anexce air percentage of 22, for example. The resultant positioningvertically of the lefthand end of the 150.

member 32 would be in accordance with the proportionality of blastfurnace gas and coke oven gas burned, and in accordance with thepercentrating. I may so shape age of each of the two gases as multipliedby or taking into account the specific excess air at which thatproportion of the total fuel were desirably to be burned. Thus theresultant movement of the lefthand end of the member 32 might be thesummation of the effect of burning 25% of the fuel as blast furnace gasat 18% excess air, and 75% of the fuel as coke oven gas at 22% excessair.

If I allowed the lefthand end of the floating member 32 to be effectivedirectly for vertical positioning of the link '42, then I would havesuch a condition as I have just explained,'effective in relation withthe steam flow as indicated relative to the relation index 46 and forpositioning the contact bar 44. If the proper relation existed betweenB. t. u. output from the boiler as measured by the steam flow therefromin relation to the total air flow, where a portion of the total air flowrepresented products of combustion of blast furnace gas at 18% excessair and products of combustion of coke oven gas at.22% excess air, thenthe indicator 44 would show the desired relation condition on the index46, and the contacts 4'7, 48 would remain open circuited. I provide,however, through the cam 35 intermediate the member 32 and the link 42,the possibility of burning the fuels in any relative proportions; eachwith the same or different percentage of excess air; and the total witha different excess of air at one boiler rating than at another boilerthe cam 35 that the excess of air, except for that related to therelative proportionality of the two fuels burned, is the same at onerating as at another rating; or I may so shape the cam 35 to have anydesirable relationship between the excess of air at one rating and thatat another rating.

To bring out more clearly the principle of my invention, I will definewhat I mean by "flow effect and illustrate the same in connection withthe fuels mentioned. The term flow effect as I use it denotes therelative effects on a differential pressure responsive device of theproducts of combustion produced by the burning. at an equal rate of heatgeneration of the fuel in question and of carbon with the theoreticalamount of air necessary for complete combustion, and considered at thelower heating value, and may be expressed by the formula:

Flow eEect=MI i QQLQL Where W=Weight of products of combustion per poundof fuel. Sp. vol.=Specific volume of products of combustion at 800. F.(considered as the average temperature at point of measurement)" H=Lowerheating value of the fuel being compared to carbon constant which givesa flow effect of 100 when burning carbon with the theoretical amount ofair.

In Fig. 2 I illustrate by means of curves the flow.

From the formula, considering. carbon burned with the theoretical amountof air necessary, we obtain a flow effect of 100. The flow effect ofother fuels burned with the theoretical amount of air necessary, or atany specified percentage of excess air, may becalculated from theformula or read directly from a curve similar to that of Fig. 2, and theflow effect value so obtained may be compared to that of carbon orrelative to 'each other.

For instance, coke oven gas burned at 20% excess air has a flow effect(from the curve) of 119. Blast furnace gas burned at 20% excess air(from the curve) shows a flow effect of 1'79. The relation between thetwo flow effects, namely 1'79/l19=1.5, which is the correction factor itwould be necessary to apply to the air flow reading if the air flow hadbeen calibrated and adjusted for a condition wherein coke oven gas onlywere being burned, and the operation were suddenly switched to a burningof blast furnace gas only. This on the assumptiomof course, that theoperator would desire to maintain a condition of 20% excess air for eachof the two fuels.

I show the indexes 18, 23, 41, 65 each graduated from zero to 100%. Ifblast furnace gas alone is being burned, and at, for example, 20% excessair, then the reading on the index 18 will be the same as the reading onthe index 23, showing that the air flow is correct in relation to the B.t. u. output of the boiler-furnace unit. This regardless of rate ofoperation between zero and 100% maximum.

If coke oven gas alone is being burned, then the reading on the index 23will not necessarily correspond to the reading on the index 18, but thereading on the index 41 will be the same as the reading on the index 18,for the reading on the index 41 will be the reading of the index 23compensated for the fact that there is no blast furnace gas beingburned, but all coke oven gas being burned. The reading on the index 23for this example relative to that of the preceding paragraph will be inthe relation of 1.5, or the relation of flow effects; namely, 179/119.The compensating effect upon the member 32 by the meter 55 will be 1.5,so that the reading on the index 41 will be the reading of the index 23times 1.5. This on the assumption that the blast furnace gas and cokeoven gas were each burned at the same percentage of excess air, and thatthe cam 35 were of uniform rise characteristic, wherein the verticalpositioning of the indicator end of the beam 38 was directlyproportional to the vertical movement of the left-hand end of the member32.

If now the coke oven gas were to be burned at an excess air of 22%, andthe blast furnace gas at 18%, then the correction relation would not be1.5, but the ratio of fiow effects 1'78 to 121' or 1.46.

If now the blast furnace gas and coke oven gas are burned simultaneouslybut in varying proportions, then the movement of the beam 38 relativetothe index 41 is in accordance with the proportions of the two fuelsburned, as well as the excess airat which each of the two fuels isburned. Furthermore, through the introduction of the cam 35 I may departfrom such definite value of excess air at which each of the fuels is tobe burned, and provide that the excess air be radically different at onerating than at another, regardless of the proportionality of the fuelsburned at thetwo ratings.

Ihave thus broadly conceived apparatus for advising a relation between ameasure of the out-' put of a furnace and a measure of the air flowthrough the furnace, with such relation taking into account thevariation in flow effect of the products of combustion resulting fromthe burning of a plurality of fuels simultaneously in varyingproportions in the furnace. Furthermore, the advice of the indicatorsand relation of indications may be used for manual or automatic controlof the supply of air to the furnace. In addition, an adjustment isarranged whereby the compensating effect through the relation ofindications may be varied, dependent upon and in accordancewithcalorific value or other variation in composition or characteristicof the burning of the individual fuels. Additionally, the fuels may beburned in any relative proportion from zero to maximum rate for each orall of the plurality of fuels and a correction dependent upon varyingflow effect is effective regardless of rate of operation of the furnace.l

l I provide that the fuels may be burned at predetermined percentage ofexcess air which may differ the one fuel from another, and that at thesame time, and regardless of the proportionality of the fuels as burned,the total excess of air over that theoretically required for perfectcombustion may differ, one rating from another rating, in the operationof the boiler. I provide adjustments whereby such relation may be variedas desired.

.1 primarily provide a meter for indicating the rate of flow of steamfrom a boiler as a measure of the output of a furnace. I further providea meter for measuring the rate of supply of one fuel to the furnace.Still further, I provide an air flow meter for measuring the total airflow I and products of combustion through the furnace, and Iinter-relate the measurements and indications to the end that I advisethe maintenance or departure from predetermined relation of indicationsfor the purpose of guidance in hand or automatic control of combustion,and specifically of the supply of air for combustion to the furnace.

I illustrate and describe a control of the air supplied for combustionto a furnace through the usage of a relation between a measure of theair flow and a measure of one of a plurality of fuels burnedsimultaneously and in varying. proportions in the furnace, and showpossible manual or automatic control of the air supply from suchindications, and with adjustment for changing calorific value or othercharacteristic for compensation of the fuels being so burned.

While I have illustrated and described a preferred embodiment of myinvention wherein two fuels, namely blast furnace gas and coke oven as,are fed simultaneously in varying proportions from zero to maximum ofeither of the fuels to the furnace of a steam generating boiler, it isto be understood that I am not to be limited thereto, for the inventioncontemplates broalily the burning of a plurality of fuels regardless oftype or number simultaneouslyfor the heating of a furnace and regardlessof the type of furnace or the service for which its heating is to beused. a

7 What I claim as new, and desire'to secure by Letters Patent of theUnited States, is:

1.-'The method of controlling the air supplied fofl'combustion of aplurality of fuels burned simultaneously in a furnace, whichv includes,obtaining a measure of furnace output, obtaining a measure of air flow,obtaining a measure of the rate of supply of one of the fuels, applyingto the measure of air flow a compensating effect dependent on themeasure of the one fuel, de-

evaeee termining the relation between the measure of furnace output andthe compensated measure of air flow, and subjecting the air supply tocontrol in accordance with the departure of said relation from apredetermined value.

2. The method of controlling the air supplied for combustion of aplurality of fuels burned simultaneouslyin a furnace, which includes,obtaining a measure of furnace output, obtaining a measure of air flow,applying to themeasure of air flow a compensating effect representativeof total heat supplied the furnace by one of the fuels, determining therelation between the measure of furnace output and the compensatedmeasure of air fiow, and controlling air supply from such relationship.

3. The method of controlling the air supplied for combustion of aplurality of fuels burned simultaneously in varying proportions-in thefurmace of a vapor generator, which includes, measuring the vaporgenerated, measuring the air flow, varying the value of the measure ofair flow in accordance with heat input by one of the fuels to thefurnace, determining the relation between the measure of vapor and themeasure of air flow after the latter has been so varied, and controllingthe air supply in accordance with the departure of said relation from apredetermined value.

4. The method of controlling the air supplied for combustion of aplurality of fuels burned simultaneously in a furnace, which includes,obtaining a measure of air and gases flowing through the furnace,obtaining a measure of one only of the fuels burned, correlating suchmeas- 110 ures, and controlling air supply from the correlation.

5. Apparatus for controlling the supply of air for combustion of aplurality of fuels adapted to be burned simultaneously in a furnace andwhich may have different heating values per unit 6. A relation indicatorfor use with vapor generators heated by-combustion of a plurality offuels adapted to be burned simultaneously in varying proportions,comprising in combination, a vapor outflow meter, an air flow meter, ameter for one of the fuels supplied to the' furnace, and relationdetermining means of the vapor outflow and air flow, said fuel meteradapted to compensate the air flow meter. a

7. An indicator for use with a furnace heated by combustion of aplurality of fuels adapted to be burned simultaneously in varyingproportions, comprising in combination, an air flow meter having anindicator, and a meter of the rate of supply of one of the fuels. saidlast-named 'meter adapted to modify the effect oi the air flow adaptedto compensate the air flow meter. 150

9." A relation indicator for use with vapor generators heated bycombustion of a plurality of fuels adapted to be burned simultaneouslyin varying proportions, comprising in combination, a Vapor outflowmeter, a meter for the gaseous products of combustion flowing throughthe genorator, a meter of one of the, fuels supplied to the furnace,said fuel meter adapted to compensate the air flow meter, and relationdetermining means conjointly positioned by the vapor outflow meter andby the compensated air flow indication.

10. Apparatus for use in controlling the air supplied to a vaporgenerator heated by combustion of a plurality of different fuels burnedsimultaneously in varying proportion, comprising, in combination,relation determining means for vapor outflow and air flow, and meansresponsive to the rate of supply of one only of the fuels for providinga separate indication of air flow compensated for the said fuel supplyrate.

11. An indicator for use with a furnace heated by combustion of aplurality of fuels of different heat value adapted to be burnedsimultaneously in varying proportions, comprising, in combination, ameter of the rate of flow of gaseous products of combustion includingexcess air leaving the furnace, and a rate of flow meter for one'of thefuels adapted to compensate the first named meter.

12. The method of automatically operating a furnace adapted to be heatedby the combustion of a plurality of different fuels burnedsimultaneously in varying proportions, which includes.

supplying air for supporting combustion of the fuels at a rate in stepwith the rate of supply of one of the fuels, measuring the rate ofsupply of one only of the fuels and modifying the rate of supply of airin accordance with such measurement.

13. The method of automatically controlling the supply of air to supportcombustion of a plurality of fuels of different heat value andcomposition adapted to be burned simultaneously in varying proportion,which includes supplying air in desired excess relation to one of thefuels, and additionally controlling the supply of air in differentexcess relation to another of the fuels.

14. The combination with a furnace, of means for supplying a gaseousfuel to the furnace, means for automatically controlling the air supplyfor supporting combustion of said gaseous fuel in predetermined excessrelation at all rates of supply of the said fuel, means for supplyingsimultaneously a second gaseous fuel to the furnace, a

meter of the second fuel, and means adapted to further control thesupply of air to the furnace in predetermined excess relation to the,second fuel varying the excess relation with rate of supply of thesecond fuel.

15. The method of controlling the air supplied for combustion of aplurality of fuels burned simultaneously in a furnace, which includes,measuring the products of combustion flowing through the furnace,measuring the rate of supply of one only of the fuels burned, andcontrolling the supply of air from the measurements.

16. A relation indicator for use with a furnace heated by combustion oftwo fuels of different heat value and adapted to be burnedsimultaneously in varying proportions, comprising in combination, afurnace output meter, an air flow meter, a meter for one of the fuelssupplied to the furnace,

and relation determining means of the furnaceoutput and air flow, saidfuel meter adapted to compensate the air flow meter.

17. A relation indicator foruse with a furnace heated by combustion of aplurality of fuels adapted to be burned simultaneously in varyingproportions, comprising in combination a furnace output meter, an airflow meter, a meter for one of the fuels supplied to the furnace, andrelation determining means of the steam flow and another indication,said other indication being air flow measurement compensated by the saidfuel meter.

18. The method of operating a furnace heated by combustion of aplurality of fuels simultaneously supplied to the furnace, whichincludes, obtaining an indication of furnace output, obtaining anindication of air supplied for combustion, obtaining an indication ofrate of supply of one only of the fuels, modifying the indication of airsupplied by the indication of fuel supply, and using such modifiedindication in relation to the indication of furnace output ,to showdesirable relation therebetween or departure therefrom.

19. Apparatus for guiding the control of supply of air for combustion toa furnace, comprising in combination, a measuring device of furnaceoutput, a measuringdevice of air supply, means for comparing themeasurements relative to predetermined relation, and means responsive toa measure of one of a plurality of fuels simultaneously supplied forcombustion, said means effective in modifying the measure of air flowbefore it is compared .with the measure of furnace out-

